Detractors, meanwhile, argue that circumcision is akin to female genital mutilation. They say that the procedure is painful to newborns, that it carries a risk of complications like infection, and that it can reduce sexual pleasure later in life.

World Health Organization

There's no question that among the world's wealthy nations, the U.S. stands out when it comes to circumcision. The WHO estimates that the overall male circumcision rate in the states is somewhere between 76 and 92 percent. Most Western European countries, by contrast, have rates less than 20 percent.

But even these numbers mask considerable regional variation within countries. Check out the chart below, which uses CDC data.

One important note: the CDC numbers only count circumcisions performed in hospitals, typically immediately after the birth of a child. Some circumcisions, particularly ones performed for religious reasons, happen outside of hospitals and thus aren't captured here.

Nonetheless, there's been a clear regional divergence in hospital circumcisions since 1980. Circumcision rates in Western states have fallen sharply -- as of 2010, roughly 4-in-10 male infants were circumcised in a hospital out West. By contrast, rates in the other regions have stayed more or less flat, although with some considerable fluctuation happening in the intervening years.

Midwestern male babies have the highest hospital circumcision rate, at over 70 percent. At 66 percent the Northeast isn't far behind. Overall, the total U.S. hospital circumcision rate fell from 64.5 percent in 1979 to 58.3 percent in 2010, a decline of about 10 percent.

Survey data indicate that we may see these declines continue. A YouGov survey conducted earlier this year found that young people were more skeptical about the practice than their elders: only 33 percent of 18-to-29 year-olds said that male children should be routinely circumcised, compared to 43 percent of 30-to-44 year-olds, 52 percent of 45-to-64 year-olds, and nearly two thirds of seniors.

The age gap on circumcision is of a piece with millennials' skepticism about vaccines. Overall, men who have been circumcised don't appear to have many regrets about it: only 10 percent of circumcised men said they wished they hadn't been circumcised, according to YouGov.

Christopher IngrahamChristopher Ingraham writes about all things data. He previously worked at the Brookings Institution and the Pew Research Center. Follow